• Journal of the Korean Society of Safety
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• v.33 no.1
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• pp.103-108
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• 2018

Since tower cranes are susceptible to wind loads, the operation of the tower crane should be ceased when it exposed to a strong wind. For this reason, even in Korea, the operation limit for wind loading on the tower crane is regulated by a law. Recently the Korean law in which provided the wind speed limit to cease the tower crane operation has been revised from "instantaneous wind speed of 20 m/s" to "instantaneous wind speed of 15 m/s". Although this revision is expected to reduce safety risks in tower crane operation, some field operators still insist to lower the wind speed limit. However, in many countries "wind speed of 20 m/s" is normally used as the maximum in-service wind speed for tower cranes. Therefore, the investigation of the proper wind speed for regulation would be helpful to secure the safety of the tower crane operation under windy condition. In this study the validity of the revised wind speed limit is investigated with the surveys targeted to both tower crane practitioners and parties of concerned in construction companies, in which various questions was provided for a suitable wind speed limit and the answers were analyzed. The results showed that the revised wind speed limit is acceptable to tower crane practitioners as well as the parties of concerned in construction companies and is satisfying the structural stability requirement for in-service state tower crane. Therefore, it can be concluded that the revised wind speed limit is valid in humanly safety point of view.

• Journal of Navigation and Port Research
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• v.46 no.6
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• pp.491-500
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• 2022

It has been noted that an accurate estimation of wind loads on offshore structures such as an FLNG (Liquefied Natural Gas Floating P roduction Storage Offloading Units, LNG FPSOs) with a large topside plays an important role in the safety design of hull and mooring system. Therefore, the present study aims to develop a computational model for estimating the wind load acting on an FLNG. In particular, it is the sequel to the previous research by the author. The numerical computation model in the present study was modified based on the previous research. Numerical analysis for estimating wind loads was performed in two conditions for an interval of wind direction (α), 15° over the range of 0° to 360°. One condition is uniform wind speed and the other is the NPD model reflecting the wind speed profile. At first, the effect of sand-grain roughness on the speed profile of the NPD model was studied. Based on the developed NPD model, mesh convergence tests were carried out for 3 wind headings, i.e. head, quartering, and beam. Finally, wind loads on 6-degrees of freedom were numerically estimated and compared by two boundary conditions, uniform speed, and the NPD model. In the present study, a commercial RANS-based viscous solver, STAR-CCM+ (ver. 17.02) was adopted. In summary, wind loads in surge and yaw from the wind speed profile boundary condition were increased by 20.35% and 34.27% at most. Particularly, the interval mean of sway (45° < α <135°, 225° < α < 315°) and roll (60° < α < 135°, 225° < α < 270°) increased by 15.60% and 10.89% against the uniform wind speed (10m/s) boundary condition.

• Proceedings of the KIPE Conference
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• 2018.07a
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• pp.382-383
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• 2018

To increase the efficiency of a wind energy conversion system (WECS), the maximum power point tracking (MPPT) algorithm is usually employed. This paper proposes an optimal MPPT algorithm which tracks a sudden wind speed change condition fast. The proposed method can be implemented without the prior information on the wind turbine parameters, generator parameters, air density or wind speed. By investigating the directions of changes of the mechanical output power in wind turbine and rotor speed of the generator, the proposed MPPT algorithm is able to determine an optimal speed to achieve the maximum power point. Then, this optimal speed is set to the reference of the speed control loop. As a result, the proposed MPPT algorithm forces the system to operate at the maximum power point by using a three-phase converter. The simulation results based on the PSIM are given to prove the effectiveness of the proposed method.

• 한국신재생에너지학회:학술대회논문집
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• 2008.10a
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• pp.262-267
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• 2008

The long-term wind data are reconstructed from the short-term meteorological data to design the 4 MW offshore wind park which will be constructed at Woljeong-ri, Jeju island, Korea. Using two MCP (Measure-Correlate-Predict) models, the relative deviation of wind speed and direction from two neighboring reference weather stations can be regressed at each azimuth sector. The validation of the present method is checked about linear and matrix MCP models for the sets of measured data, and the characteristic wind turbulence is estimated from the ninety-percent percentile of standard deviation in the probability distribution. Using the Gumbel's model, the extreme wind speed of fifty-year return period is predicted by the reconstructed long-term data. The predicted results of this analysis concerning turbulence intensity and extreme wind speed are used for the calculation of fatigue life and extreme load in the design procedure of wind turbine structures at offshore wind farms.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1626-1629
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• 2005

Recently many countries have concentrated their effort on the port automation, in order to be the Hub-port, that the Ultra Large Container Ship could come alongside the Quay, in their region. As the magnitude of the container ship increase, that of the Quay crane increases from 50ton-class to 61ton-class more and more. The wind speed criteria to design the structures used in the port was upgraded from 20m/s to 40m/s due to change of the weather condition. Our laboratory could have the ability to design the wedge type rail clamp for 50ton-class Quay crane in 30m/s wind speed. Accordingly we analyzed the load condition of the Quay crane about 40m/s wind speed upgraded from 20m/s and designed the wedge type rail clamp for 50ton and 61ton-class Quay crane.

• Journal of Korean Society for Quality Management
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• v.48 no.3
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• pp.463-479
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• 2020

Purpose: The purpose of this study is to evaluate the performance of heating equipments by implementing the extreme environment in which ships navigating the ice zone are exposed and to study and apply the experimental method to infer the optimized design for each factors. Methods: It is required to verify by analysis and experiment how the environment with low temperature and wind speed implemented through the test facility affects the heating walk-way and The optimum design of the heating walk-way in that extreme environment is derived using the Taguchi technique. Results: The results of this study are as follows; It was found the effect on the condition of each factor and derive optimized conditions that satisfy the performance condition of the heating walk-way in extreme use environment. Conclusion: Ships operating in Polar waters require reliable and durable facilities for all environments during sailing.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.10
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• pp.1455-1460
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• 2014

Wind turbine generators were designed on general regulations of wind condition. At real situations, it could be different from the design conditions. There are many control methods and definitions of transient region, because an efficient wind turbine generator control logic is the important matter in generator performance and annual energy production at real conditions. In this document, the power generation sensitivity for wind speed and turbulence intensities was defined to know the sensitive transient region. Wind conditions are applied for the ranges of 7~10m/s mean wind speed and 14~20% turbulence intensity. The sensibility of HR-D86 wind generator was increased in transient region(8~10m/s) on power curve diagram through a torque control to a pitch control. And then GH-bladed simulations was performed for performance analysis of the torque mode switching in transient region on 2MW direct drive wind generator(HR-D86) which is designed IEC class II for onshore. Through the sensitivity and performance analysis, the sensitivity for real wind condition could be the performance index for an wind generator. And the torque mode switching in transient region can increase the mean power generation on HR-D86 wind turbine generator.

• Journal of Wind Energy
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• v.2 no.2
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• pp.54-60
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• 2011

A PMSG in variable speed wind turbine needs to know the position of rotor for vector control. Since the position sensor has the disadvantage in terms of cost, complexity of the system, a sensorless algorithm is needed. The sensorless strategy using the back EMF estimation is used for PMSG Wind Turbine. This algorithm is comparatively easy to implement than other strategies. This paper introduces the application of stable sensorless control for 2MW direct drive PMSG. In order to confirm the sensorless algorithm, the implementation is proceeded using 2MW direct drive PMSG from no-load condition to full-load condition. To drive 2MW PMSG artificially, 2MW PMSG connected PMSG through the mechanical coupling.

• Wind and Structures
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• v.3 no.3
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• pp.177-191
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• 2000

This paper presents an approach for evaluating directionality effects for both wind speeds and wind loads in hurricane-prone regions. The focus of this study is on directional wind loads on low-rise structures. Using event-based simulation, hurricane directionality effects are determined for an open-terrain condition at various locations in the southeastern United States. The wind speed (or wind load) directionality factor, defined as the ratio of the N-year mean recurrence interval (MRI) wind speed (or wind load) in each direction to the non-directional N-year MRI wind speed (or wind load), is less than one but increases toward unity with increasing MRI. Thus, the degree of conservatism that results from neglecting directionality effects decreases with increasing MRI. It may be desirable to account for local exposure effects (siting effects such as shielding, orientation, etc.) in design. To account for these effects in a directionality adjustment, the factor described above for open terrain would need to be transformed to other terrains/exposures. A "local" directionality factor, therefore, must effectively combine these two adjustments (event directionality and siting or local exposure directionality). By also considering the direction-specific aerodynamic coefficient, a direction-dependent wind load can be evaluated. While the data necessary to make predictions of directional wind loads may not routinely be available in the case of low-rise structures, the concept is discussed and illustrated in this paper.

• Wind and Structures
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• v.27 no.1
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• pp.29-40
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• 2018

To investigate the characteristics of the combined wind field produced by the natural wind field and the train-induced wind field on the bridge, the aerodynamic models of train and bridge are established and the overset mesh technology is applied to simulate the movement of high-speed train. Based on ten study cases with various crosswind velocities of 0~20 m/s and train speeds of 200~350 km/h, the distributions of combined wind velocities at monitoring points around the train and the pressure on the car-body surface are analyzed. Meanwhile, the difference between the train-induced wind fields calculated by static train model and moving train model is compared. The results show that under non-crosswind condition, the train-induced wind velocity increases with the train speed while decreases with the distance to the train. Under the crosswind, the combined wind velocity is mainly controlled by the crosswind, and slightly increases with the train speed. In the combined wind field, the peak pressure zone on the headstock surface moves from the nose area to the windward side with the increase of wind velocity. The moving train model ismore applicable in analyzing the train induced wind field.